Another closeup of the South face. The concrete under the sign is quite chipped, but the window "panels" appear to have escaped rust. Maybe they're not metal, like the ones on the East face?
Now a closeup of the East face. The roof sign is blank on this side.
Lower half of the East face. You can plainly see that this was the door in (you can see the holes where the door handle and lock were). Strangely the panels appear to have been filled in, presumably to make the door more resistant to vandalism.
Stepping back from the East face for an all-in shot.
Took me a while to figure out this one. Presumably taken while standing against the railing in the previous shot, this appears to be the North face on the left and the West face on the right. The Roof sign is blank on the West face (which overlooks the Blackwall Tunnel), but filled in on the North face. The West face is the only part of the box with the original window frames in, and probably the one that escaped the most vandalism (on account of it directly overlooking the Tunnel).
This affords a good close-up of how the standard Police Box window frames were constructed. It can plainly be seen from the close-up below that they were metal strips, with the vertical ones overlapping the horizontal ones. Now imagine these painted white.
So there you go. The East face was the door. The North and South faces had "Fire Brigade Control" on the roof signs, whilst the West and East facing signs were blank. And the West face still had the window frames.
Sadly these photos are probably all that remains of these unique variants of the Metropolitan Police Box, as the Blackwall North Box (and it's twin on the Tunnel entrance south of the Thames) were demolished in the 1980s.